Originally Posted by Sal@Evolve
Love it when you get all technical!
Serious note - you are completely correct here with respect to the fuel factor table and lambda aims.
The lambda will aim to what ever you set it - but it can only aim so much.
If the fuel factor table (10x10 fuel side) map is not altered correctly and the fuel scaling factor is not calculated correctly with respect to the size of the injectors then the aim will always be aiming but never achieving because the deviation is simply too large.
Our own supercharged car has been tested in 0 degC, 5-8 degC and 25+ degC. Our aim is 12.2 AFR. We achieve very close to it what ever the ambient temperature is (there is a limit where physics will take over but they are big). The reason is because the fuel scaling and fuel factor table has been correctly set which is derived from continual testing and retesting.
Now, for the fueling to go leaner with colder denser air implies that the DME is infact not at all intelligent and is like that of a Bosch Motronic 1.1!
A denser cooler charge will actual require more fuel and if that did happen then the AFR will be maintained.... like we would hope.
An intelligent DME will not allow this unless the base calibration for fuel is too far out for the aim to reach as mentioned above.
It's all quite logical.
I am by the way not going to comment on if the AFR is lean or rich on any graphs. Who knows... could be down to placement of the probe. Could be a break in the pipe drawing in air? Who knows?
(opens packet of silk cut silver and begins to smoke)
exactly, w.out all the tech BS; we tune for a target, and the ECU will adapt but only w/in a certain window of scale. Now if the car is tuned rather lean, I can't see that being beneficial once the car is heatsoaked or in stop and go 100 degree days, the car is going to want to pull timing and negate any benefits. Outside of that window and we have now put a window in the block.
And I guess another thing to note is if subject car has cats or not as this will def change values read at the tailpipe. BUt this is all the more reason that if I was gonna boost this car, and really extract all the power I can, I would def put a wideband 02 up near the collectors to get an "accurate" value